Saponin extraction

ABSTRACT

Crude aqueous extracts of Quillaja saponaria Molina containing at least the QS-21 main peak and 2018 component, wherein the ratio of 2018 component/QS-21 main peak is ≤0.075, as measured by UV absorbance at 214 nm, methods for obtaining such extracts and related aspects.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage Application under 35 U.S.C. § 371of International Application No. PCT/EP2018/083233, filed Nov. 30, 2018,which: 1) claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 62/593,555, filed Dec. 1, 2017 and 2) claimspriority under 35 U.S.C. § 119(b) to EP Application No. 17209796.6,filed Dec. 21, 2017. All of the above-listed applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

The present application generally relates to saponin extracts, inparticular crude aqueous extracts of Quillaja saponaria Molina, methodsfor their manufacture and to associated aspects.

BACKGROUND OF THE INVENTION

Adjuvants are included in vaccines to improve humoral and cellularimmune responses, particularly in the case of poorly immunogenic subunitvaccines. Similar to natural infections by pathogens, adjuvants rely onthe activation of the innate immune system to promote long-lastingadaptive immunity.

The Adjuvant System 01 (AS01) is a liposome-based adjuvant whichcontains two immunostimulants, 3-O-desacyl-4′-monophosphoryl lipid A(3D-MPL) and QS-21 (Garcon and Van Mechelen, 2011; Didierlaurent et al.,2017). 3D-MPL is a non-toxic derivative of the lipopolysaccharide fromSalmonella minnesota which is a TLR4 agonist) and QS-21 is a naturalsaponin extract from the bark of the South American tree Quillajasaponaria Molina (Kensil et al., 1991; Ragupathi et al., 2011). AS01 isincluded in the recently developed vaccines for malaria(RTS,S—Mosquirix®) and Herpes zoster (HZ/su—Shingrix®), and in multiplecandidate vaccines in development against pathogens such as humanimmunodeficiency virus and Mycobacterium tuberculosis.

AS01 injection results in rapid and transient activation of innateimmunity in animal models. Neutrophils and monocytes are rapidlyrecruited to the draining lymph node (dLN) upon immunization. Moreover,AS01 induces recruitment and activation of MHCII^(high) dendritic cells(DC), which are necessary for T cell activation (Didierlaurent A. M. etal., 2014). Some data are also available on the mechanism of action ofthe components of AS01. 3D-MPL signals via TLR4, stimulating NF-κBtranscriptional activity and cytokine production and directly activatesantigen-presenting cells (APCs) both in humans and in mice (De Becker etal., 2000; Ismaili et al., 2002; Martin et al., 2003; Mata-Haro et al.,2007). QS-21 promotes high antigen-specific antibody responses and CD8⁺T-cell responses in mice (Kensil and Kammer, 1998; Newman et al., 1992;Soltysik et al., 1995) and antigen-specific antibody responses in humans(Livingston et al., 1994). Because of its physical properties, it isthought that QS-21 might act as a danger signal in vivo (Lambrecht etal., 2009; Li et al., 2008). Although QS-21 has been shown to activateASC-NLRP3 inflammasome and subsequent IL-1β/IL-18 release (Marty-Roix,R. et al., 2016), the exact molecular pathways involved in the adjuvanteffect of saponins have yet to be clearly defined.

As with any component of a product which is approved as a humanmedicament, production of QS-21 requires the use of approvedmanufacturing processes and careful control of final composition toensure that it meets the required specification. Modification ofexisting processes requires costly and time consuming re-validation, yetdeviations from specification also result in waste. There is acontinuing need for robust methods for the manufacture of QS-21 and forQS-21 material of defined composition.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a crude aqueousextract of Quillaja saponaria Molina containing at least the QS-21 mainpeak and 2018 component, wherein the ratio of 2018 component/QS-21 mainpeak is 0.075, as measured by UV absorbance at 214 nm.

In a second aspect, the present invention provides a crude aqueousextract of Quillaja saponaria Molina containing

QS-21AV1

QS-21AV2

1856 component:

and2002 component:

(collectively referred to as QS-21 main peak components),and 2018 component:

wherein the ratio 2018 component/QS-21 main peak components is 0.075, asmeasured by UV absorbance at 214 nm.

In a third aspect, the present invention provides a method for preparinga crude aqueous extract of Quillaja saponaria Molina comprising thefollowing steps:

a) selecting Quillaja saponaria Molina material having an appropriate2018 component content

b) preparing an aqueous extract from the material under conditionswherein 2018 component generation is controlled.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 : HPLC chromatogram of a crude aqueous Quillaja saponaria Molinabark extract

FIG. 2 : HPLC-UV chromatogram of a crude aqueous Quillaja saponariaMolina bark extract

FIG. 3 : UPLC-UV chromatogram of a crude aqueous Quillaja saponariaMolina bark extract

FIG. 4 Tabulation of experimental conditions and observed impact on 2018component/QS-21 main peak ratio

FIG. 5 Surface plot of observed impact on 2018 component/QS-21 main peakratio arising from pH and temperature conditions

FIG. 6 Impact of temperature on 2018 component to QS-21 main peak ratioover time at pH 3.8

DETAILED DESCRIPTION

As mentioned previously, any component of a product which is authorisedas a human medicament requires the use of approved manufacturingprocesses and careful control of final composition to ensure that itmeets the required specification. Deviations from specification resultin waste. However, safety and efficacy investigation relies upon thetesting of defined compositions, therefore adaptation of componentspecifications introduces risk. Modification of existing processesrequires costly and time consuming re-validation.

The present inventors have found that crude aqueous extracts of Quillajasaponaria Molina vary in composition, in particular with respect to acomponent referred to herein as the 2018 component, and that it isdifficult to separate excess 2018 component by applying existingapproved manufacturing processes. Consequently, the present inventionprovides methods for achieving a crude aqueous extract of Quillajasaponaria Molina of a defined composition, suitable for the preparationof consistent purified extracts following further processing.

Variation in composition may be due to natural deviations in the sourcematerial and/or due to conditions applied when extracting the saponinsto obtain the crude aqueous extract.

The inventors developed a crude aqueous extract of Quillaja saponariaMolina of defined composition, in particular in terms of the 2018component content as compared to the content of components of principalinterest. Said crude aqueous extract advantageously provides a suitablestarting material with which to obtain a purified saponin extract whichis particularly suitable for use as an immunostimulant providing anefficient immune response and an acceptable level of reactogenicity whenformulated with an antigen and administered to a subject.

Quil A is a saponin preparation isolated from the South American treeQuillaja saponaria Molina and was first described as having adjuvantactivity by Dalsgaard et al. in 1974 (“Saponin adjuvants”, Archiv. fürdie gesamte Virusforschung, Vol. 44, Springer Verlag, Berlin, p243-254). Purified fractions of Quil A have been isolated by HPLC whichretain adjuvant activity without the toxicity associated with Quil A(see, for example, EP0362279). Various fractions have been found to haveadjuvant activity, such as QS-7, QS-17, QS-18 and QS-21, although theirtoxicity varies considerably.

By the term ‘saponin extract’ as used herein is meant an extract ofQuillaja saponaria Molina.

By the term ‘triterpenoid glycosides’ as used herein is meant an entityor entities having a triterpenoid core derivatised by sugars which areattached via glycosidic bonds.

By the term ‘2018 component’ is meant the triterpenoid glycosidesidentified as ‘2018’ in FIG. 3 . Suitably the 2018 component in theUPLC-UV methods described herein may be identified with a retention timeof approximately 5.8 min, and the primary component of the peak having amonoisotopic molecular weight of 2017.9. The primary 2018 component hasbeen identified as having the putative structure

by MS/MS.

By the term ‘1988 component’ is meant the triterpenoid glycosidesidentified as part of the QS-21 main peak in FIG. 3 and having amonoisotopic molecular weight of 1987.9. The 1988 component may consistof QS-21A V1:

and QS-21A V2

By the term ‘1856 component’ is meant the triterpenoid glycosidesidentified as part of the QS-21 main peak in FIG. 3 and having amonoisotopic molecular weight of 1855.9. The 1856 component may consistof:

By the term ‘2002 component’ is meant the triterpenoid glycosidesidentified as part of the QS-21 main peak in FIG. 3 and having amonoisotopic molecular weight of 2001.9. The 2002 component has beenidentified as having the putative structure:

by MS/MS.

Limitations of the MS/MS technique in differentiating certain branching,stereochemistry and isomeric sugar species (e.g. apiose and xylose)means that some structures are putative and based on an assumedconserved core. Putative structures should therefore be taken to meanthe actual structure of the entity which has otherwise been identified,in the event the putative structure is incorrect.

Monoisotopic molecular weights are determined by negative ionelectrospray mass spectrometry.

By the term ‘QS-21 main peak’ is meant the triterpenoid glycosidesidentified as ‘QS-21’ and ‘QS-21 Main’ in FIG. 2 or FIG. 3 respectively.Suitably QS-21 has the principal molecular weight components of 1855.9,1987.9 and 2001.9 m/z The QS-21 main peak may consist primarily ofQS-21AV1:

QS-21A V2:

1856 component:

and2002 component:

By the term ‘Preceding peak’ is meant the peak immediately preceding theQS-21 main peak in the HPLC-UV methods described herein (see FIG. 2 ).

By the term ‘dried’ is meant that substantially all solvent has beenremoved. A dried extract will typically contain less than 5% solvent w/w(such as less than 5% water w/w). Suitably the dried extract willcontain 100 ppm or less acetonitrile (w/w).

The crude aqueous extract of Quillaja saponaria Molina is obtained byaqueous extraction (but need not be in aqueous form, e.g. it maysubsequently have been dried, subjected to solvent exchange orreconstituted into a different solvent).

In a first aspect, the present invention provides a crude aqueousextract of Quillaja saponaria Molina containing at least the QS-21 mainpeak and 2018 component, wherein the ratio of 2018 component/QS-21 mainpeak is ≤0.075, as measured by UV absorbance at 214 nm. Suitably theratio of 2018 component/QS-21 main peak is ≤0.064, as measured by UVabsorbance at 214 nm. Desirably the ratio of 2018 component/QS-21 mainpeak is at least 0.005, such as at least 0.01 as measured by UVabsorbance at 214 nm.

Suitably the Preceding peak to QS-21 main peak ratio is 0.45 or lower,in particular 0.4 or lower (as determined by HPLC-UV absorbance at 214nm). The Preceding peak to QS-21 main peak ratio may be 0.05 or higher,in particular 0.1 or higher (as determined by HPLC-UV absorbance at 214nm).

Typically the crude extract is a bark extract of Quillaja saponariaMolina. Accordingly, suitably the crude extract is obtained fromQuillaja saponaria Molina bark.

Suitably the QS-21 main peak content in an aqueous solution of crudeaqueous extract of Quillaja saponaria Molina is at least 1 g/L, such asat least 2 g/L, especially at least 2.5 g/L and in particular at least2.8 g/L (e.g. as determined by UV absorbance relative to a controlsample of known concentration).

In a second aspect, the present invention provides a crude aqueousextract of Quillaja saponaria Molina containing:

QS-21AV1

QS-21AV2

1856 component:

and2002 component:

(collectively referred to as QS-21 main peak components),and 2018 component:

wherein the ratio of 2018 component/QS-21 main peak components is 0.075,as measured by UV absorbance at 214 nm.

Suitably the ratio 2018 component/QS-21 main peak components is 0.064,as measured by UV absorbance at 214 nm. Desirably the ratio of 2018component/QS-21 main peak components is at least 0.005, such as at least0.01 as measured by UV absorbance at 214 nm.

Suitably the Preceding peak to QS-21 main peak ratio is 0.45 or lower,in particular 0.4 or lower (as determined by HPLC-UV absorbance at 214nm). The Preceding peak to QS-21 main peak ratio may be 0.05 or higher,in particular 0.1 or higher (as determined by HPLC-UV absorbance at 214nm).

Typically the crude extract is a bark extract of Quillaja saponariaMolina. Accordingly, suitably the crude aqueous extract of the inventionis obtained from Quillaja saponaria Molina bark.

Suitably the QS-21 main peak content in an aqueous solution of crudeaqueous extract of Quillaja saponaria Molina is at least 1 g/L, such asat least 2 g/L, especially at least 2.5 g/L and in particular at least2.8 g/L (e.g. as determined by UV absorbance relative to a controlsample of known concentration).

Saponin Extraction

In a third aspect, there is provided a method for preparing a crudeaqueous extract of Quillaja saponaria Molina comprising the followingsteps:

a) selecting Quillaja saponaria Molina material having an appropriate2018 component content,

b) preparing an aqueous extract from the material under conditionswherein 2018 component generation is controlled.

Suitably, the Quillaja saponaria Molina material is Quillaja saponariaMolina bark.

Typically, prior to the extraction, the Quillaja saponaria Molina plantmaterials are dried and milled. The harvested plant materials may beleft to dry naturally and/or are dried partially or fully by beingsubject to heat. Suitably, when subjected to heating the dryingtemperature is in the range of 30-100° C., such as around 80° C., andmay last for a few hours to 8 hours. Once dry, said plant materials aremilled.

Any aqueous extraction process can be applied to obtain a crude aqueoussaponin extract of Quillaja saponaria Molina in accordance with theinvention. Solvent used for extraction will be substantially water butmay include small amounts of other materials. The solvent will typicallyconsist essentially of water, desirably the solvent is water. Extractionmay take place in successive steps and be performed in a temperatureranging from 50° C. to 80° C. and may last from a couple of hours to 20hours, such as 2 to 20 hours. Saponin crude extracts typically comprisea mixture of saponin species and non-saponin compounds, such as sugars,salts, polyphenols (tanins), solids in suspension and other lowermolecular weight compounds. Prior to separating the different componentsin order to reach a purified saponin extract having a desired saponinprofile, typically by a series of different chromatographic purificationsteps, the saponin crude extracts may be subject to clarification inorder to remove impurities made of non-saponin compounds. Suitably,polymeric adsorbents, such as polyvinylpolypyrrolidone (PVPP), known tocomplex polyphenols, and/or clay-derived materials, such as bentonite,may be added to saponin crude extracts. Saponin crude extracts mayadditionally be concentrated, for example by nanofiltration orultrafiltration. In order to obtain saponin crude extracts having alonger shelf life, said extracts may also be pasteurized, using hightemperature, such as ranging from 40° to 95° C., suitably 60 to 90° C.,especially about 86° C. Suitably pasteurization is performed for 10minutes to 1 hour, more suitably 40 to 50 minutes. Antimicrobial agentsmay be used. An example of an antimicrobial agent is an antibacterialagent, such as sodium benzoate. A preservative may also be used.Suitably the crude aqueous extract is substantially sterile, and moresuitably, sterile.

Suitably the step a) of selecting Quillaja saponaria Molina materialhaving an appropriate 2018 component content comprises testing the 2018component content of the Quillaja saponaria Molina material and/ordetermining the 2018 component content which would be obtained duringaqueous extraction from the Quillaja saponaria Molina. Typically, thestep of determining the 2018 component content which would be obtainedduring aqueous extraction from the Quillaja saponaria Molina comprisesperforming a small-scale extraction and determining the 2018 componentcontent in the resulting extract. Suitably the small-scale extraction isperformed on less than 500 g, such as less than 50 g, of Quillajasaponaria Molina material.

Suitably step b) is performed on at least 25 kg, such as 50 to 500 kg,such as 100 to 400 kg and in particular 200 to 300 kg of Quillajasaponaria Molina material.

While developing a process suitable for preparing a crude aqueousextract of Quillaja saponaria Molina in accordance with the invention,the present inventors observed that the pH along the process, incombination with high temperature, such as when pasteurizing, should beclosely monitored and controlled. In particular, the inventors observedthat combining low pH with high temperature may influence the stabilityof saponins and thus impact the saponin profile of an extract beingprocessed, while high temperature on its own only triggered limitedimpact. Therefore, a balance between pH and temperature needs to bereached when preparing a saponin crude extract, depending on the saponinprofile desired. In particular, the present inventors observed that theratio of 2018 component/QS-21 main peak increases when a hightemperature is combined with a low pH. Therefore, when using hightemperature, such as during pasteurization, in combination with a lowpH, such as when using a preservative like sodium benzoate, the timespent at high temperature should be limited to the maximum extentpossible. For example, in order to quickly reach the pasteurizationtemperature, a heat exchanger may be used and/or the pasteurized crudeaqueous extract of Quillaja saponaria Molina be cooled down rapidly, forexample by immersion in cold water. Suitably the crude aqueous extracthas a pH of 3 to 4.5, more suitably 3.6 to 4.0.

Crude Aqueous Extract Testing

In a fourth aspect of the invention, there is provided a method fordetermining the ratio of 2018 component/QS-21 main peak in a crudeaqueous extract of Quillaja saponaria Molina, said method comprising thesteps of:

-   -   (i) determining the 2018 component content in the crude aqueous        extract of Quillaja saponaria Molina by UPLC-UV absorbance at        214 nm;    -   (ii) determining the QS-21 main peak content in the crude        aqueous extract of Quillaja saponaria Molina by UPLC-UV        absorbance at 214 nm; and    -   (iii) comparing the 2018 component content to the QS-21 main        peak content to determine the ratio of 2018 component/QS-21 main        peak.

In a fifth aspect of the invention, there is provided a method foridentifying a crude aqueous extract of Quillaja saponaria Molina for usein the manufacture of a purified saponin extract, said method comprisingthe steps of:

-   -   (i) determining the ratio of 2018/QS-21 main peak by UPLC-UV        absorbance at 214 nm; and    -   (ii) selecting a crude aqueous extract having a ratio of 2018        component/QS-21 main peak which is ≤0.075.

In one embodiment, the crude aqueous extract selected in step (ii) has aratio of 2018 component/QS-21 main peak which is ≤0.064.

The invention will be further described by reference to the following,non-limiting, examples:

Example 1: Analytical Methods

HPLC-UV

Equipment

Waters Alliance 2690/2695 separations module

Waters 2487 UV Detector or 2996 PDA Detector

Vydac Protein C4 4.6×250 mm 5 um column

Mobile Phase A (MPA)—0.15% trifluoroacetic acid in water/acetonitrile(70:30 v/v)

Mobile Phase B (MPB)—0.15% trifluoroacetic acid in acetonitrile

Linear Gradient Conditions:

Flow rate Time (ml/min) % MPA % MPB 0 1 100 0 30 1 78.6 21.4 33 1 14.385.7

10 ul of sample is injected. UV detection is set at 214 nM.

Using a blank injection for reference, integration of peaks in thechromatogram provides a total absorbance. Peak of interest (e.g. QS-21main peak) is compared to total absorbance to determine peak content asa percentage.

UPLC-UV

Equipment

Waters Acquity UPLC

Waters Acquity Tunable UV Detector

Waters Acquity BEH C18 2.1×100 mm 1.7 um column

Mobile Phase A (MPA)—0.025% acetic acid in water/acetonitrile (70:30v/v)

Mobile Phase B (MPB)—0.025% trifluoroacetic acid in water/acetonitrile(30:70 v/v)

Linear Gradient Conditions:

Flow rate Time (ml/min) % MPA % MPB 0 0.5 88 12 10.2 0.5 65.7 34.3 11.20.5 10 90 13.2 0.5 10 90

Column temperature 28 degrees C. 10 ul of sample is injected. UVdetection is set at 214 nM.

Using a blank injection for reference, integration of peaks in thechromatogram provides a total absorbance. Peak of interest (e.g. QS-21main peak) is compared to total absorbance to determine peak content asa percentage.

Example 2: Crude Aqueous Extract of Quillaja saponaria Molina

A crude aqueous bark extract was separated by reverse phase HPLC using aC4 column and gradient elution: mobile phase A—water/acetonitrile, 7/3v/v with 0.15% trifluoroacetic acid; mobile phase B—acetonitrile with0.15% trifluoroacetic acid. UV detection was at 214 nm.

Crude aqueous bark extract samples are diluted as necessary withpurified water. PVPP (60 mg/mL) was added, the mixture stirred forapproximately 30 minutes, and then centrifuged to separate the PVPPresin from the supernatant.

The supernatant was then analysed to provide an HPLC-UV chromatogram.

FIG. 1 provides a representative example of an HPLC-UV chromatogram. Thepeak corresponding to the QS-21 fraction is indicated.

Example 3: UPLC-UV of an Aqueous Saponin Crude Bark Extract of Quillajasaponaria Molina Tree

A sample of crude aqueous bark extract of Quillaja saponaria Molina wasanalysed by the HPLC-UV and UPLC-UV methods described in Example 1.

FIG. 2 provides the results of the HPLC-UV and FIG. 3 provides theresults of the UPLC-UV.

By determining the peak area for the particular components (QS-21 mainpeak, 2018 component or Preceding peak) it is possible to calculate theratios of the components in the crude extract.

Example 4: Effect of pH and Temperature on the 2018 Component/QS-21Ratio

Multiple samples of crude aqueous extract of Quillaja saponaria Molinawere prepared according to the methods described herein. On eachoccasion, the temperature, pH or quantity of sodium benzoate was variedduring the pasteurisation phase and the change in 2018 component/QS-21main peak ratio was measured after 3 hours. The results are provided inFIG. 4 . The impact of pH and temperature variation is representedgraphically in FIG. 5 . The impact of different temperatures over timeat constant pH 3.8 is illustrated in FIG. 6 .

Temperature was found to be directly proportional to the 2018component/QS-21 main peak ratio, except at or below 40° C. during this 3hour range tested, where the ratio does not seem to change regardless ofthe pH or sodium benzoate conditions. pH was found to be inverselyproportional to the 2018 component/QS-21 main peak ratio, especially atlower pHs.

Sodium benzoate only had a minor effect on the 2018 component/QS-21 mainpeak ratio at elevated temperatures.

In summary, it was found that varying pH and temperature had asubstantial impact on the 2018 component/QS-21 main peak ratio, withhigher temperatures and lower pH increasing the ratio.

Consequently, in order to obtain a crude aqueous extract of Quillajasaponaria Molina with appropriate levels of 2018 component, carefulselection of Quillaja saponaria Molina raw material and processing in amanner which limits excessive 2018 component generation is necessary.

Example 5: Large Scale Production of Crude Aqueous Extract of Quillajasaponaria Molina Having Defined 2018 Component Composition

Bark Selection

Sample lots of approximately 37 g were taken from a range of batches ofQuillaja saponaria Molina bark material. The samples were separatelysubjected to aqueous extraction at around 65° C. for approximately 5hours. The extract was treated with PVPP, filtered and concentrated. pHwas adjusted to 3.9 before the addition of sodium benzoate (0.1%) andpasteurisation performed at 86° C. for 45 minutes.

2018 component (using UPLC-UV) and Preceding peak content (usingHPLC-UV) was then determined. Based on the results, batches of Quillajasaponaria Molina bark material were selected for use in full scaleextraction.

Although individual batches may not meet target specification, tomaximise yield it is possible to combine individual batches which areoutside target specification with other batches (e.g. high content withlow content) such that an overall average within target specification isachieved.

Main Extraction

Approximately 280 kg of Quillaja saponaria Molina bark material selectedfor 2018 component content was subjected to aqueous extraction at around70° C. for at least 2 hours. Following extraction, the pH was adjustedto 3.8. The extract was treated with PVPP, filtered and concentrated. pHwas verified and adjusted again if necessary before the addition ofsodium benzoate (0.1%) and pasteurisation performed at 86° C. for 45minutes. Pasteurised material was quickly cooled to minimise the time atelevated temperature, thereby providing a solution of crude aqueousextract of Quillaja saponaria Molina.

Crude aqueous extract was analysed by HPLC-UV (Preceding peak/QS21 mainpeak ratio) and UPLC-UV (2018 component/QS21 main peak ratio).

Bark selection and control of pH and temperature exposure ensured thatcrude bark extract consistently met the desired specification. In theabsence of bark selection and control of pH and temperature exposure,crude aqueous extract frequently failed to meet specification.

The use of the process as described in Example 5 can consistentlyprovide a crude aqueous bark extract of Quillaja Saponaria Molina havinga defined ratio of 2018 component/QS-21 main peak, such as consistentlys 0.075, and presenting a chromatographic profile comparable to thechromatogram shown in FIG. 3 .

BIBLIOGRAPHY

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The invention claimed is:
 1. A crude aqueous extract of Quillajasaponaria Molina containing:

1856 component:

and 2002 component:

(collectively referred to as QS-21 main peak components), and 2018component:

wherein the ratio of 2018 component/QS-21 main peak components is≤0.075, as measured by UV absorbance at 214 nm, and wherein the crudeaqueous extract comprises sodium benzoate.
 2. The crude aqueous extractof claim 1, wherein the ratio of 2018 component/QS-21 main peakcomponents is at least 0.005, as measured by UV absorbance at 214 nm. 3.The crude aqueous extract of claim 1, wherein the QS-21 main peakcontent in an aqueous solution of crude aqueous extract of Quillajasaponaria Molina is at least 1 g/L.
 4. The crude aqueous extract ofclaim 1, wherein the ratio of 2018 component/QS-21 main peak componentsis <0.064, as measured by UV absorbance at 214 nm.
 5. The crude aqueousextract of claim 1, wherein the ratio of 2018 component/QS-21 main peakcomponents is at least 0.01, as measured by UV absorbance at 214 nm. 6.The crude aqueous extract of claim 1, wherein the Preceding peak toQS-21 main peak ratio is 0.45 or lower as determined by HPLC-UVabsorbance at 214 nm.
 7. The crude aqueous extract of claim 1, which isin aqueous form.
 8. The crude aqueous extract of claim 1, which is indried form.
 9. The crude aqueous extract of claim 1, wherein the crudeaqueous extract is sterile.
 10. The crude aqueous extract of claim 1,wherein the crude aqueous extract has a pH of 3.0 to 4.5.
 11. A methodfor preparing a crude aqueous extract of claim 1 comprising thefollowing steps: a) selecting Quillaja saponaria Molina material havingan appropriate 2018 component content, b) preparing an aqueous extractfrom the material under conditions wherein 2018 component generation iscontrolled, and c) adding sodium benzoate to the crude aqueous extract.12. The method of claim 11, wherein the step a) of selecting theQuillaja saponaria Molina material having an appropriate 2018 componentcontent comprises determining the 2018 component content which would beobtained during aqueous extraction from the Quillaja saponaria Molina.13. The method of claim 12, wherein the step a) of determining the 2018component content which would be obtained during aqueous extraction fromthe Quillaja saponaria Molina comprises performing a small-scaleextraction and determining the 2018 component content in the resultingextract.
 14. The method of claim 13, wherein the small-scale extractionis performed on less than 500 g, such as less than 50 g, of the Quillajasaponaria Molina material.
 15. The method of claim 11, wherein step b)is performed on at least 25 kg, of the Quillaja saponaria Molinamaterial.
 16. The method of claim 11, wherein the crude aqueous extractof Quillaja saponaria Molina is treated with polyvinylpolypyrrolidone(PVPP).
 17. The method of claim 16, wherein the pH of the crude aqueousextract of Quillaja saponaria Molina is maintained within a pH rangeduring PVPP treatment.
 18. The method of claim 11, wherein the methodcomprises the further step c) of pasteurizing the crude aqueous extractof Quillaja saponaria Molina.
 19. The method of claim 18, wherein thepasteurization is performed at 40 to 95° C.
 20. The method of claim 18,wherein the pH of the crude aqueous extract of Quillaja saponaria Molinais maintained within a pH range during pasteurization.
 21. The methodaccording to claim 18, wherein sodium benzoate is added to the crudeaqueous extract of Quillaja saponaria Molina prior to pasteurization.22. The method of claim 18, wherein the pasteurization is performed for10 minutes to 1 hour.
 23. The method of claim 18, wherein afterpasteurization the crude extract is actively cooled.
 24. The method ofclaim 18, wherein after pasteurisation the crude aqueous extract ofQuillaja saponaria Molina is filtered.
 25. The method of claim 24,wherein the pH of the crude aqueous extract of Quillaja saponaria Molinais maintained within a pH range during filtration.
 26. The method ofclaim 18, wherein after pasteurisation the crude aqueous extract ofQuillaja saponaria Molina is concentrated.
 27. The method of claim 26,wherein the pH of the crude aqueous extract of Quillaja saponaria Molinais maintained within a pH range during concentration.
 28. The method ofclaim 17, wherein the pH range is 3.0 to 4.5.
 29. The method of claim11, wherein the Quillaja saponaria Molina material is Quillaja saponariaMolina bark.
 30. The method according to claim 11, wherein the crudeaqueous extract of Quillaja saponaria Molina contains at least the QS-21main peak and the 2018 component, wherein the ratio of 2018component/QS-21 main peak is ≤0.075, as measured by UV absorbance at 214nm.